[GRASS-user] RST - how does it chooses from near points?

[M S]

I cant answer the question of how the v.surf.rst module choses points,
but I can say that with the use of r.in.xyz you can control this quite
well.

For example, (and relating to the last question) you can use different
methods to assign values to the cells from ASCII import.  Meaning if
you have multiple points in a cell, and you only want the values that
are the minimum in the cell, use the 'method=min' option.
Alternatively, you can use 'mean' and 'max' for other applications as
well.

then you would r.to.vect the data, as 3d points and then interpolate
with v.surf.rst.  If I recall right, by doing this r.in.xyz, it cut
out about 35% of the processing time for v.surf.rst in my application.

Especially for LiDAR data, I found the r.in.xyz module to be nothing
short of spectacular.  With the 'method=n' option, and an r.report
<raster> unit=p, you can see the percent distribution of points per
cell to help set cell size.  These are some great tools!


Mark


On 5/27/08, Carlos Guâno Grohmann <carlos.grohmann at gmail.com> wrote:
> It just came to me: if I have a vector map to be interpolated by RST,
> how does the algorithm chooses between points that are very close to
> each other?
> And if I have more than one point with the same coordinates, but
> different values?
>
> thks all
>
> Carlos
>
> --
> +-----------------------------------------------------------+
>  Carlos Henrique Grohmann - Guano
>  Geologist M.Sc - Doctorate Student at IGc-USP - Brazil
> Linux User #89721 - carlos dot grohmann at gmail dot com
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